A trend in detergent formulating is to reduce the amount of surfactant and to replace these petrochemical derived ingredients with highly weight efficient ingredients selected from cleaning and soil release polymers, sequestrants and enzyme cocktails. Typically some surfactant is retained in the composition and the work horse surfactant linear alkyl benzene sulphonate (LAS) is frequently a key part of the surfactant blend. The polymer ethoxylated polyethylene imine may be used as one of the weight efficient ingredients. Suitable compositions are taught, for example, in WO 09/153184.
To meet consumer preference it is desirable to thicken concentrated detergent liquids. However, the thickening system does not contribute to the cleaning performance of a product as used in a washing machine. There is some evidence that it can under certain conditions even reduce cleaning performance. A weight efficient thickening system with low cleaning negatives is desirable.
Hydrophobically modified alkali swellable emulsion (HASE) copolymers are known as synthetic associative thickeners. These copolymers typically contain a backbone comprising a major part of residues of randomly distributed methacrylic acid (MAA) and ethylacrylate (EA) monomers. Inserted into this backbone are a small proportion of hydrophobically modified groups, usually less than 3 mol %. The monomers to form these hydrophobic groups are sometimes referred to as surfmers or associative monomers. Due to its structure, the copolymer, when dissolved in an alkaline aqueous liquid, induces a variety of interacting forces such as hydrophobic, hydrogen bonding, electrostatic, etc and this modifies the rheology of the liquid. It is further known that the HASE copolymers and their thickening behaviour may be further modified by use of crosslinkers. HASE copolymers are usually synthesized via emulsion polymerization.
U.S. Pat. No. 5,015,711 (Coatex) discloses a thickening terpolymer of the MAA/EA/surfmer type.
WO 2014/082955 (Unilever) and WO 2014/082874 (Unilever) disclose thickened liquid laundry compositions containing thickening polymer derived from ethyl acrylate (EA), methacrylic acid (MMA), maleic anhydride (MA) and surfmer components. The compositions contain surfactant and ethoxylated polyamine (EPEI).
It would be desirable to provide a weight efficient thickening system which exhibits a reduced negative impact on the cleaning performance of a thickened aqueous detergent liquid.